Radiological Mimicries of Brain Tumors in Epilepsy Surgery: Five Case Reports

Objective: Brain tumors such as gangliogliomas and dysembryoplastic neuroepithelial tumors (DNET) are frequent epileptogenic lesion in pediatric epilepsy surgery. MRI can be used to identify such dysontogenetic tumors by characteristic features such as juxtacortical growth, cystic components, signal changes because of demyelination and neoplastic neuronal cells or glial cells, which can be seen on MRI. We report on five clinical cases of neurosurgically treated patients with refractory epilepsies and the radiological suspicion of dysontogenetic tumors which were not confirmed neuropathologically.

Material and Methods: Retrospective study on clinical data and MRI findings. All Patients underwent at least one high-resolution MRI and surface video-EEG-monitoring over several days. The operations were discussed and planned in interdisciplinary case conferences.

Results: Two patients are girls (15 and 18 years old at the time of the operation) and three patients are boys (3, 5 and 12 years). First seizures occurred between 4 months and 12 years. Patient 1: MRI suspected a tumor of the amygdala, neuropathology (08/2007) revealed mMCD type II (Palmini & Lüders classification). Patient 2: MRI suspected a dysontogenetic tumor, neuropathology (11/2004) revealed meningoangiomatosis. Patient 3: MRI suspected DNT with surrounding FCD-like, tumor-associated changes, neuropathology (02/2017) revealed FCD type IIb (focal cortical dysplasia). Patient 4: MRI suspected a dysontogenetic tumor (probably DNET), neuropathology (04/2018) revealed FCD type IIb (focal cortical dysplasia). Patient 5: MRI suspected a dysontogenetic tumor or low grade glioma, neuropathology (03/2019) revealed encephalitis with T-lymphocyte infiltrates and microglial nodules compatible with Rasmussen`s encephalitis.

Conclusion: Our five case reports demonstrate that non-tumorous epileptogenic lesions can present with a tumor-like appearance on MRI. This post-operative etiology must be respected during post-surgical care of these patients, and can change the post-operative course dramatically. Furthermore, also these cases emphasize that epilepsy surgical aspects should be taken into consideration when (supposedly) epileptogenic tumors are operated.